3D sonar uncovers skeleton of Civil War battleship

Looking like the weathered skeleton of some ancient dinosaur, the
rusting remains of an American Civil War battleship have been imaged in their underwater grave by 3D
sonar.

The USS Hatteras sank during battle
with the CSS Alabama in 1863, coming to rest in 17 metres of water in the Gulf
of Mexico, 30 kilometres off the coast of Galveston, Texas. One hundred and fifty
years later, the bones of the iron-hulled paddle-wheel steamship have been mapped
by the US National Oceanic
and Atmospheric Administration (NOAA).

NOAA made the scans after local underwater photographer Jesse
Cancelmo noticed that recent storms had shifted some of the sediment and
sand that covered the wreck. The main image above shows the curved tooth-like
outline of the stern on the right. The paddle-wheel shaft stretches from the top
to the bottom of the picture, where the remains of the port paddle wheel lie
crumpled like the bones of a skeletal hand. More than half of the ship still
lies beneath the seabed.

This side-on view of the paddle-wheel shaft also shows the ship's broken stern in the distance (Image: James Glaeser/Northwest Hydro/NOAA)

"Most shipwreck survey maps are two-dimensional and
based on observations made by sight, photographs or by feeling around in murky
water while stretching a measuring tape," said James Delgado of NOAA's
Office of National Marine Sanctuaries. "Thanks to the high-resolution
sonar, we have a three-dimensional map that not only provides measurements and
observations, but the ability for researchers and the public to virtually swim
through the wreck's exposed remains and even look below the surface at
structure buried in loose silt."

The Hatteras can't be disturbed due to its status as US navy
property and a war grave - two of its engine-room crew killed in the battle
with the Alabama are believed to lie buried inside the hull. This made the 3D
sonar scan particularly well suited to mapping the wreck, because it's completely
hands-off.